drivers/scsi/st_options.h

   1 /*
   2    The compile-time configurable defaults for the Linux SCSI tape driver.
   3
   4    Copyright 1995-2000 Kai Makisara.
   5
   6    Last modified: Sat Mar 11 10:32:00 2000 by makisara@kai.makisara.local
   7 */
   8
   9 #ifndef _ST_OPTIONS_H
  10 #define _ST_OPTIONS_H
  11
  12 /* The driver does not wait for some operations to finish before returning
  13    to the user program if ST_NOWAIT is non-zero. This helps if the SCSI
  14    adapter does not support multiple outstanding commands. However, the user
  15    should not give a new tape command before the previous one has finished. */
  16 #define ST_NOWAIT 0
  17
  18 /* If ST_IN_FILE_POS is nonzero, the driver positions the tape after the
  19    record been read by the user program even if the tape has moved further
  20    because of buffered reads. Should be set to zero to support also drives
  21    that can't space backwards over records. NOTE: The tape will be
  22    spaced backwards over an "accidentally" crossed filemark in any case. */
  23 #define ST_IN_FILE_POS 0
  24
  25 /* If ST_RECOVERED_WRITE_FATAL is non-zero, recovered errors while writing
  26    are considered "hard errors". */
  27 #define ST_RECOVERED_WRITE_FATAL 0
  28
  29 /* The "guess" for the block size for devices that don't support MODE
  30    SENSE. */
  31 #define ST_DEFAULT_BLOCK 0
  32
  33 /* The tape driver buffer size in kilobytes. */
  34 #define ST_BUFFER_BLOCKS 32
  35
  36 /* The number of kilobytes of data in the buffer that triggers an
  37    asynchronous write in fixed block mode. See also ST_ASYNC_WRITES
  38    below. */
  39 #define ST_WRITE_THRESHOLD_BLOCKS 30
  40
  41 /* The maximum number of tape buffers the driver tries to allocate at
  42    driver initialisation. The number is also constrained by the number
  43    of drives detected. If more buffers are needed, they are allocated
  44    at run time and freed after use. */
  45 #define ST_MAX_BUFFERS 4
  46
  47 /* Maximum number of scatter/gather segments */
  48 #define ST_MAX_SG      16
  49
  50 /* The number of scatter/gather segments to allocate at first try (must be
  51    smaller or equal to the maximum). */
  52 #define ST_FIRST_SG    8
  53
  54 /* The size of the first scatter/gather segments (determines the maximum block
  55    size for SCSI adapters not supporting scatter/gather). The default is set
  56    to try to allocate the buffer as one chunk. */
  57 #define ST_FIRST_ORDER  5
  58
  59
  60 /* The following lines define defaults for properties that can be set
  61    separately for each drive using the MTSTOPTIONS ioctl. */
  62
  63 /* If ST_TWO_FM is non-zero, the driver writes two filemarks after a
  64    file being written. Some drives can't handle two filemarks at the
  65    end of data. */
  66 #define ST_TWO_FM 0
  67
  68 /* If ST_BUFFER_WRITES is non-zero, writes in fixed block mode are
  69    buffered until the driver buffer is full or asynchronous write is
  70    triggered. May make detection of End-Of-Medium early enough fail. */
  71 #define ST_BUFFER_WRITES 1
  72
  73 /* If ST_ASYNC_WRITES is non-zero, the SCSI write command may be started
  74    without waiting for it to finish. May cause problems in multiple
  75    tape backups. */
  76 #define ST_ASYNC_WRITES 1
  77
  78 /* If ST_READ_AHEAD is non-zero, blocks are read ahead in fixed block
  79    mode. */
  80 #define ST_READ_AHEAD 1
  81
  82 /* If ST_AUTO_LOCK is non-zero, the drive door is locked at the first
  83    read or write command after the device is opened. The door is opened
  84    when the device is closed. */
  85 #define ST_AUTO_LOCK 0
  86
  87 /* If ST_FAST_MTEOM is non-zero, the MTEOM ioctl is done using the
  88    direct SCSI command. The file number status is lost but this method
  89    is fast with some drives. Otherwise MTEOM is done by spacing over
  90    files and the file number status is retained. */
  91 #define ST_FAST_MTEOM 0
  92
  93 /* If ST_SCSI2LOGICAL is nonzero, the logical block addresses are used for
  94    MTIOCPOS and MTSEEK by default. Vendor addresses are used if ST_SCSI2LOGICAL
  95    is zero. */
  96 #define ST_SCSI2LOGICAL 0
  97
  98 /* If ST_SYSV is non-zero, the tape behaves according to the SYS V semantics.
  99    The default is BSD semantics. */
 100 #define ST_SYSV 0
 101
 102
 103 #endif